/* =============================================================
 * Your Grandmother's guide to Algorithms
 * =============================================================
 *
 * Copyright (c) 2007, Saverio Miroddi
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright 
 *       notice, this list of conditions and the following disclaimer in the 
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the SaverioMiroddiSoftware nor the names of its 
 *       contributors may be used to endorse or promote products derived from 
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *  
 * ---------------------------
 * BitArrayOutputStream.java
 * ---------------------------
 *
 */
package huffman;

import java.io.ByteArrayOutputStream;

public class BitOutputStream
{
	private static final int BITS_PER_BYTE = 8;
	
	private ByteArrayOutputStream _output;
	private boolean[] _currByte;
	private int _bitPtr;
	
	public BitOutputStream()
	{
		_output = new ByteArrayOutputStream();
		_currByte = new boolean[BITS_PER_BYTE];
		_bitPtr = 0;
	}
	
	public void append(BitPath path)
	{
		boolean[] appending = path.getBits();
		
		for (int appendingPtr = 0; appendingPtr < appending.length; )
		{
			int available = BITS_PER_BYTE - _bitPtr;
			int toWrite = appending.length - appendingPtr; 
			
			if (toWrite < available) {
				System.arraycopy(appending, appendingPtr, _currByte, _bitPtr, toWrite);
				appendingPtr += toWrite;
				_bitPtr += toWrite;
			}
			else {
				System.arraycopy(appending, appendingPtr, _currByte, _bitPtr, available);
				appendingPtr += available;
				_bitPtr += available;
				flushByteIfNeeded();
			}
		}
	}

	private void flushByteIfNeeded() 
	{
		if (_bitPtr > 0) {
			int dest = 0;
			
			for (int i = 0; i < _currByte.length; i++) {
				if (_currByte[i])  // we have a 1 
					dest |= 1 << (BITS_PER_BYTE - 1 - i);
			}
					
			_output.write(dest);
			
			_bitPtr = 0;
		}
	}
	
	public byte[] toByteArray()
	{
		flushByteIfNeeded();
		return _output.toByteArray();
	}
}
